DPP4 and type 2 diabetes mellitus: On the other hand, clinical guidelines for pharmacologic treatment in type 2 diabetes [5] recommend metformin (biguanide) as first-line pharmacological treatment, followed by a second-line drug such as sulfonylureas, glucagon-like peptide (GLP-1) receptor agonists, sodium-glucose cotransporter-2 (SGLT2) inhibitors, and dipeptidyl peptidase 4 (DPP-4) inhibitors, among others.